LONDON — The number of deaths from measles has fallen by 79 percent worldwide since 2000, thanks mainly to mass vaccination campaigns, but more than 350 children still die from the disease every day, global health experts said on Thursday.

In a report on global efforts to “make measles history,” the United Nations Children’s Fund, or Unicef, the World Health Organization and other health agencies said the fight against measles was being hampered not by a lack of tools or knowledge, but by a lack of political will to get every child immunized against measles.

“Without this commitment, children will continue to die from a disease that is easy and cheap to prevent,” said Robin Nandy, Unicef’s head of immunization.

The report said measles vaccination campaigns and a global increase in routine vaccine coverage had saved about 20.3 million young lives from 2000 to 2015.

But coverage is patchy, and, in some countries, a majority of children are not vaccinated. In 2015, about 20 million babies missed their shots, and about 134,000 children died from the disease.

According to the report, half of all unvaccinated babies and 75 percent of deaths from measles occur in the Democratic Republic of Congo, Ethiopia, India, Indonesia, Nigeria and Pakistan .

Measles is a highly contagious virus that can spread by direct contact or through the air. It can be prevented with a widely available and inexpensive vaccine.

Published by Unicef, the W.H.O., the Centers for Disease Control and Prevention; and Gavi, the Vaccine Alliance; the report said that outbreaks of measles in various countries — caused by gaps in immunization — are still a major problem.

In 2015, outbreaks were reported in Egypt, Ethiopia, Germany, Kyrgyzstan and Mongolia, the report said, with those in Germany and Mongolia mostly affecting older people. Those outbreaks, the report went on to say, highlighted the need to immunize young people who had missed out on vaccinations.

Measles, the report added, also tends to flare up during conflicts or humanitarian crises, evidenced by outbreaks last year in Nigeria, Somalia and South Sudan.

A version of this article appears in print on , on Page A10 of the New York edition with the headline: Despite Gains, Measles Kills 350 Each Day. Order Reprints | Today’s Paper | Subscribe